1. Field of the Invention
The invention relates generally to the fields of statistical multiplexing and distribution of content such as e.g., digital video. In one exemplary aspect, the invention relates to improving the performance of a digital cable network by utilizing information gained via the demultiplexing process to enforce and maintain a quality of service policy.
2. Description of Related Technology
So-called “Quality of Service” or QoS refers generally to resource reservation and allocation control mechanisms. For example, QoS when implemented can provide different priority to different data flows, or guarantee a certain level of performance to a data flow.
The goal of QoS is to improve the user experience and a network's ability to deliver predictable results for sensitive applications such as audio, video, and voice applications. Elements of network performance within the scope of QoS often include bandwidth (throughput), latency (delay), and error rate. There are generally two broad classes of QoS: data reliability and temporal reliability. Each makes different demands on network technologies.
QoS guarantees become increasingly crucial when network capacity is limited, since inter alia there is increased risk of degraded service or content when the network capacity is approached. An everyday analogy might be a person's morning commute to work; when the network (streets and highways) approach their capacity, there is increased risk that an accident, auto breakdown, inclement weather, or just the delays associated with starting and stopping large volumes of cars will very significantly impact that person's arrival time. Conversely, when the highways and roads are lightly used, the risk of such significant delays are minimal. Commuter lanes (i.e., those specifically reserved for carpools, etc.) can be thought of as a QoS guarantee of sorts; those commuters utilizing these lanes will have effectively unimpeded travel and access, thereby all but guaranteeing a much more timely arrival at work.
QoS utilization and allocation of resources have long been implemented and described in the prior art for various other types of networks including, inter alia, packet switched networks. For example, U.S. Pat. No. 5,488,609 to Hluchyj, et al. issued Jan. 30, 1996 and entitled “DYNAMIC RATE ADJUSTMENT FOR OVERLOAD CONTROL IN COMMUNICATION NETWORKS” is exemplary of one such implementation. It discloses a device (500) and method (300) which provide for management of resource allocation on selected links in a connection-oriented communication network such that existing connections may share the burden of freeing up resources for accommodating new connections. The rate of a connection is dynamically adjusted, on a connection-by-connection basis, using information on the status of each link broadcast throughout the network. Links are marked based on control information in the link state, and the in-call rate adjustment is based on negotiable Quality of Service (QoS) parameters.
U.S. Pat. No. 7,012,891 to Chandran, et al. issued Mar. 14, 2006 and entitled “METHOD AND APPARATUS FOR APPLYING QUALITY OF SERVICE TO MULTICAST STREAMS TRANSMITTED IN A CABLE NETWORK” discloses a method and apparatus for providing quality of service parameters for transmissions of multicast streams on a cable network is provided. A cable network headend connects an external network to a hybrid fiber coax or cable network. The cable network headend maintains a table of cable modems with entries associating each cable modem with one or more quality of service parameters. Virtual cable modem entries are created for multicast streams when indications of quality of service for multicast streams are received by the cable network headend. Multicast packets arriving at the cable network headend are processed using the stored quality of service parameters for the corresponding multicast stream. The multicast packets may then be transmitted, queued, or dropped depending on the specified parameters and traffic shaping or policing algorithms.
QoS utilization and allocation of resources has also been implemented and described in telecommunications networks. For example, U.S. Pat. No. 5,825,779 to Putnins, et al. issued Oct. 20, 1998 entitled “PBX NETWORKING WITH QUALITY OF SERVICE CONTROL” discloses a networking node for interconnecting a local telephone switch such as a private branch exchange (PBX) with other such switches through other nodes, with respective internodal multichannel digital transmission links interconnecting the various nodes, provides service for both data and voice messages. The networking node provides at least two levels (one of which may be zero) of compression for voice messages and permits one of those levels to be preselected for all voice messages from the switch with which the node is associated to a predetermined one or more of the other nodes in the network. A look-up table is stored in memory within the node to control the assignment of particular levels of compression to particular destinations.
U.S. Pat. No. 5,581,544 to Hamada, et al. issued Dec. 3, 1996 and entitled “METHOD AND APPARATUS FOR EVALUATING IN ATM MULTIPLEXING APPARATUS IN WHICH PRIORITY CONTROL IS PERFORMED AND FOR CONTROLLING CALL ADMISSIONS AND OPTIMIZING PRIORITY CONTROL ON THE BASIS OF THE EVALUATION” discloses a probability transition matrix St that expresses a multiplexing process which includes nested threshold priority control and classified priority control. A state equation using the matrix St is solved by substituting therein upper and lower bounds of a probability distribution of a cell arrival count at in an average time series, to calculate a probability distribution of a cell length in a buffer. From the thus calculated cell length probability distribution, the QoS is evaluated on a priority class basis. Based on the QoS evaluation, optimization of call admission control and priority control is accomplished.
QoS utilization and allocation of resources has also been implemented and described in broadband networks. For example, U.S. Pat. No. 7,283,803 to Karaoguz, et al. issued Oct. 16, 2007 and entitled “LOCATION-AWARE APPLICATION BASED QUALITY OF SERVICE (QOS) VIA A BROADBAND ACCESS GATEWAY” discloses a system and method supporting access to multimedia information based upon user-defined quality of service criteria is disclosed. A broadband access gateway may coordinate network behavior during the transition of an access device among communication pathways having different available capacities. Adjustments in bitrates and levels of compression may be made based upon the user-defined quality of service criteria. The user may be notified when network conditions disallow support for the desired quality of service, and may choose to override selected criteria. The user-defined quality of service criteria may be stored within the gateway and associated with a user, or may be located in the access device and accessible to the gateway.
U.S. Pat. No. 6,856,786 to Belostotsky, et al. issued Feb. 15, 2005 and entitled “QUALITY OF SERVICE SCHEDULING SCHEME FOR A BROADBAND WIRELESS ACCESS SYSTEM” discloses a dynamic quality of service maintenance system for use with a broadband wireless or cable access system comprising a plurality of wireless modems and a wireless hub, the dynamic quality of service maintenance system maintaining adequate bandwidth for the wireless modems based upon the services provided to the wireless modems by the broadband wireless access system.
U.S. Pat. No. 5,944,795 to Civanlar issued Aug. 31, 1999 and entitled “CLIENT-SERVER ARCHITECTURE USING INTERNET AND GUARANTEED QUALITY OF SERVICE NETWORKS FOR ACCESSING DISTRIBUTED MEDIA SOURCES” discloses an improved client-server architecture of the present invention utilizes the advantages of known QoS networks to provide guaranteed quality of service, security, and a charge mechanism for handling requests initiated over a packet network, such as the Internet, for access to distributed media sources. Such media sources may be independent of the QoS network provider and may be located by browsing the Internet. A method of operating a client-server network enables the system level merger of the Internet and a guaranteed QoS network, such as the public switched telephone network, in order to provide the users with a complete information superhighway today. It will appear to the average user that the Internet and the QoS network are fused together. Thus, when a user, connected to the Internet, selects an application that requires functionalities offered by the telephone network, such as guaranteed QoS delivery of media information or customized billing, the Internet-resident application will communicate information to a server, which will in turn initiate a session over the QoS network for delivery of the required information to the client using client information transmitted from the client (or from the application) to the server over the established Internet session. The client information may include a client account number, login and password, and/or phone number to enable the server to establish the switched network connection to the client. Accordingly, media sources which are separate and independent from the QoS network provider may be accessed using a secure, guaranteed QoS network in a manner providing for ease of identification and billing.
Despite the foregoing plethora of different approaches to QoS, there exists no effective QoS implementation in content-based (e.g., cable, fiber optic, or satellite) networks that enforces QoS policy within the subscriber's premises and which allows for efficient bandwidth utilization. Specifically, in current cable or satellite networks, a subscriber's consumer premises equipment (CPE) has no way to characterize the QoS properties of a variable bitrate (VBR) program stream, nor to ensure a QoS will be maintained when a user selects a particular program stream. Static policies are typically employed in such cases; for instance, the instantaneous bitrate of an HD (high definition) program stream might average 5-8 Mbps, yet have only very occasional peaks up to say 15 Mbps. Under a static policy, such peaks would need to be accounted for (lest the content be “clipped” and accordingly potentially degraded in quality that is perceivable by a viewer), and hence a static bandwidth allocation of 15 Mbps would be applied for the entire duration of that program stream. Hence, there is substantial bandwidth utilization inefficiency in existing static-policy based systems where QoS is required.
Statistical Multiplexing—
In traditional digital television networks, digital programming is collected at a central location, assembled in multiple program transport streams and transported to other intermediate locations in the network for further downstream transportation to the consumer's premises equipment (CPE). In recent years, statistical multiplexing techniques have been employed in an increasing number of central locations (e.g., cable headends) to efficiently create the centrally aggregated program multiplexes. As is well known, statistical multiplexing (colloquially referred to as “stat mux”) is a technique used to efficiently pack multiple programs within a transport stream. This technique relies on the principle that the instantaneous bandwidth required to transmit a given program fluctuates over time, typically based on the ease of compression of the video content. This makes bandwidth-efficient transmission of multiple programs possible as a multiplex by sharing the allocated bitrate. Because the bitrate peaks of separate program streams do not occur simultaneously, a group of programmers can share an allocated bitrate that is smaller than the sum of the bitrate peaks of the program streams carried. Furthermore, the bitrate contribution each individual program stream is typically controlled (commonly referred to as rate shaped) to provide both a safety factor and even greater efficiencies. Conventional approaches to statistical multiplexing have recognized that the greater the number of programs in a multiplex (i.e., “pool size”), the better the chances of using bandwidth efficiently.
A variety of approaches to statistical multiplexing are in evidence under the prior art. For example, U.S. Pat. No. 5,708,664 to Budge, et al. issued Jan. 13, 1998 entitled “STATISTICAL MULTIPLEXING” discloses a transmitter for transmitting a plurality of digital signals through a plurality of channels, the channels having a predetermined total allocated bitrate. The transmitter includes a plurality of encoders each associated with one channel, a multiplexer for receiving the encoded digital signals and for transmitting the encoded signals as a stream of data, and operable for adjusting the distribution of the bitrate allocation between and among the encoded signals, and a processing device for providing an indication of a target quality and an actual quality for each channel and for causing the multiplexer to repeatedly adjust the distribution of the bitrate allocation in response to differences between the indicated actual quality and the indicated target quality for each channel so as to equalize differences between the actual and target quality across at least some of the channels. By grouping encoders together in “statistical multiplex groups”, and making real time decisions about the bitrate requirements for those encoders, bitrate can be allocated to maximize picture quality for the group. For a variety of different picture sources in a statistical multiplex group, to achieve a target picture quality the bitrate requirements of each will vary with coding difficulty. Thus, a channel within the statistical multiplex group that is experiencing little difficulty in encoding its picture can free bits to channels that are having greater difficulty. The effect is to smooth the picture quality and subjectively improve it.
U.S. Pat. No. 6,285,716 to Knee, et al. issued Sep. 4, 2001 entitled “VIDEO COMPRESSION” discloses a method to manipulate an MPEG-2 or other compressed video stream as separate information bus and coefficient streams. The information bus stream contains motion vector information but also information derived from a previous decoding operation for use in a subsequent coding operation. Processing in the coefficient domain enables bitrate conversion without decoding to the pixel level and also ostensibly simplifies the combination of MPEG layers.
U.S. Pat. No. 6,577,682 to Brightwell, et al. issued Jun. 10, 2003 entitled “VIDEO PROCESSING SYSTEM ALSO COMPRESSING CODING DECISION DATA” discloses a method in which an MPEG2 decoded video signal is accompanied by a representation of the coding decisions to aid downstream re-encoding. The representation is MPEG compliant bit modified as an attempt to reduce the number of bits.
U.S. Pat. No. 6,792,045 to Matsumura, et al. issued Sep. 14, 2004 entitled “IMAGE SIGNAL TRANSCODER CAPABLE OF BIT STREAM TRANSFORMATION SUPPRESSING DETERIORATION OF PICTURE QUALITY” discloses An MPEG2 decoder portion decodes an input bit stream and outputs a digital decoded image while extracting coding information and supplying the same to a control portion. An MPEG2 encoder portion re-encodes the digital decoded image output from the MPEG2 decoder portion. Coding information supplied from the control portion is reflected on a coding parameter in re-encoding. Transcoding between the MPEG2 standard and the DV standard can also be executed by arranging a decoder or an encoder corresponding to the DV standard in place of either the MPEG2 decoder portion or the MPEG2 encoder portion.
U.S. Pat. No. 6,795,506 to Zhang, et al. issued Sep. 21, 2004 entitled “METHODS AND APPARATUS FOR EFFICIENT SCHEDULING AND MULTIPLEXING” discloses techniques and mechanisms for scheduling and multiplexing compressed bitstreams. A compressed bitstream includes bitrate information describing the bitrate of video data. The bitrate information is used to ostensibly improve the scheduling and multiplexing efficiency of compressed bitstreams. Compressed video data can be transmitted over communication channels at bitrates that comply with available channel bandwidth.
United States Patent Publication 20010055336 to Krause, et al. published Dec. 27, 2001 and entitled “COMPRESSED-VIDEO RE-ENCODER SYSTEM FOR MODIFYING THE COMPRESSION RATIO OF DIGITALLY ENCODED VIDEO PROGRAMS” discloses a compressed video decoder/encoder (re-encoder) system for varying the compression ratio of a compressed video program. The composite re-encoder system implements tightly coupled elements for decoding and encoding compressed video data implementing techniques of header forwarding and utilizing an architecture in which a shared motion compensator supports both decoding and encoding operations simultaneously. The re-encoder system may be introduced in a statistical multiplexer for generating a compressed video data stream multiplex suitable for use in cable distribution and other video distribution systems.
United States Patent Publication No. 20020085584 to Itawaki, et al. published Jul. 4, 2002 entitled “STATISTICAL MULTIPLEX SYSTEM, STATISTICAL MULTIPLEX CONTROLLER AND METHOD OF STATISTICAL MULTIPLEX” discloses a statistical multiplex system, a statistical multiplex controller and a method of statistical multiplex, which can assign bitrates to program data and auxiliary data for purposes of image quality. A statistical multiplex system is provided with: a plurality of image encoders for encoding a plurality of program data; an information encoder for encoding the auxiliary data; a multiplexing apparatus for multiplexing output thereof, and a statistical multiplex controller for controlling each of the image encoders and the information encoder. The statistical multiplex controller is made to set the bitrate to be assigned to the information encoder first, and to assign the remaining bitrates to each of the image encoders.
Based on the foregoing, there exists a salient need in a digital content-based network for methods and apparatus that provide the ability to obtain and utilize QoS data for the variable bit program streams in order to, inter alia, implement and enforce QoS policy within the subscriber's premises environment (e.g., home network), while also allowing for efficient bandwidth utilization within the network so as to support delivery of a large number and density of digital content services to a single CPE. Ideally, such methods and apparatus would be readily practiced with existing infrastructure and network protocols, thereby making its implementation within extant content delivery networks (and associated CPE currently in use with subscribers) simple and very low cost.